The transmitter was installed in 1942 at a purpose-built site near Crowborough in southeast England. This was equipped with other mediumwave and shortwave transmitters, which also used the Aspidistra name, being known as ASPI 2, ASPI 3, ASPI 4, etc. However, when the name Aspidistra was used on its own it always referred to the original mediumwave transmitter (ASPI 1).

After the war, Aspidistra and other transmitters at Crowborough were used for BBC External Service broadcasts to Europe. The station closed in 1982.

In addition to its high power, Aspidistra could be re-tuned quickly to a new frequency (position on the dial). This was of great use in its secret wartime work and was unusual for a mediumwave transmitter, as they generally operate on a fixed frequency throughout their working life.

Its antenna was three guyed masts, each 110 m (360 ft) tall. The 1940s Art Deco style transmitter building was in an underground shelter which had been excavated by a Canadian army construction unit. Power for the transmitter was supplied from a single large Crossley-Premier 16 cylinder heavy oil engine.[2]

Alongside the original Aspidistra, other mediumwave and shortwave transmitters were installed over the years. These included two Doherty 250 kW mediumwave units, whose outputs could be combined to give 500 kW on a single frequency.[3]

Two 100 kW shortwave transmitters made by General Electric (USA) operated at the Crowborough site from 1943 until the 1980s.[4]

Starting in 1943, Aspidistra was used to disrupt German nightfighter operations against Allied bombers over Germany. German radar stations broadcast the movements of the bomber streams en route to targets during RAF Bomber Command's Battle of Berlin. As part of their strategies to misdirect the German fighters, German-speaking RAF operators impersonated these German ground control operators, sending fake instructions to the nightfighters. They directed the nightfighters to land or to move to the wrong sectors. This interference to enemy RT and WT was known as "Dartboard"[5] As German operational procedures changed to prevent impersonation so the British copied them, bringing in WAAFs when the Germans used female operators.[6]

During Allied air raids, German radio transmitters in target areas were switched off to prevent their use as navigational aids by the enemy. However, such transmitters were very often connected into a network, and broadcast the same content as other transmitters which were not switched off.

When a targeted transmitter switched off, Aspidistra began transmitting on its frequency, initially retransmitting the German network broadcast as received from an active station. This would cause German listeners to believe the original station was still broadcasting. Aspidistra operators would then insert demoralizing false content and pro-Allied propaganda into the broadcast. This content was considered especially effective, as it appeared to be coming from official German sources.

The first such intrusion was carried out on 25 March 1945. On 30 March 1945 Aspidistra intruded on the Berlin and Hamburg stations, warning that the Allies were trying to spread confusion by sending false telephone messages from occupied towns to unoccupied towns. On 8 April 1945 "Aspidistra" intruded on the Hamburg and Leipzig stations to warn of forged banknotes in circulation. On 9 April 1945 there were announcements encouraging people to evacuate to seven bomb-free zones in central and southern Germany. All these announcements were false.

German radio stations tried announcing "The enemy is broadcasting counterfeit instructions on our frequencies. Do not be misled by them. Here is an official announcement of the Reich authority." However, Aspidistra broadcasts included similar announcements, leaving the listeners confused.[8]

Although mainly intended for the military and propaganda transmissions described above, Aspidistra was also used during the war for some BBC broadcasts to Europe. After 1945, Aspidistra was used exclusively by the BBC. Frequencies used included 1122 kHz (1945-1950), 1340 kHz (1950-1962), 809 kHz (until 1978), 1295 kHz (1962-1978) and 1088 kHz (1972-1978). After reorganisation of the mediumwave band in 1978, the frequencies used were 648 and 1296 kHz.[9]

Despite its exclusive post-war use by the BBC, the Crowborough station remained formally in the hands of the Foreign Office (from 1968, the Foreign and Commonwealth Office, FCO), and its staff were members of the Diplomatic Wireless Service (later known as the FCO's Communications Department and then the Communications Engineering Department) rather than the BBC.

Aspidistra made its final transmission on 28 September 1982, the honour of pressing the "off" key for the last time going to Harold Robin, the Foreign Office engineer who had been responsible 40 years earlier for purchasing the transmitter in the USA and setting up the station at Crowborough.

The station was dismantled in 1984. Two years later, following extensive modifications, the bunker that housed the Aspidistra transmitter was commissioned by the Home Office as one of the 17 sites in England and Wales to be used as seats of regional government in the event of a nuclear attack.[10]

From 1988, Sussex Police used parts of the site, purchasing all of it in 1996 for use as a training facility.[11]

In 2007, Building No. 3 (known as "the cinema" because of its design similarities with pre-war Art Deco cinemas), which had once housed ASPI 3 and ASPI 6, was designated a Grade II listed structure because of its historic and architectural interest. The designation notes that it is "a remarkably intact and unaltered building through which one can understand its function as an early 1940s transmitter hall".[12]

A reported offer to donate the Aspidistra transmitter to London's Science Museum was not taken up and it was scrapped. A number of valves (tubes) and a large tuning coil were saved by FCO engineers and are now on display in the foyer of the Orfordness station.[13] A notice there says:

One of three RF output coupling coils from the Aspidistra 1 transmitter at Crowborough in Sussex.

ASP1 was a 600 kW medium wave transmitter which was installed and commissioned with great urgency by Harold Robin during the spring and summer of 1942 and which commenced broadcasting on 8 November 1942. The transmitter was in continuous service for the next 40 years, carrying "black" propaganda to the enemy in wartime and BBC External Services to Europe in peacetime. It ceased regular transmissions on 28 September 1982 and its services were transferred to Orfordness. It was dismantled in May 1984.

This coil is preserved as a memento of a transmitter which played a large part in the wartime activities of the Political Warfare Executive. In peacetime it became part of the expanding broadcast transmission facilities provided for the External Services of the BBC by the Diplomatic Wireless Service - now the Communications Engineering Department of the Foreign and Commonwealth Office.

^Brown, Anthony Cave (1976). The Secret War Report of the OSS. Berkeley. ISBN978-0-425-03253-4. Its high power and ability to rapidly switch frequency made it extremely useful for such activities; its power output alone gave it a reach well into Europe with a signal clarity that frequently confused German listeners, who thought it might be broadcasting from a local source.